What is SuppressWarnings (“unchecked”) in Java?

Question

Sometime when looking through code, I see many methods specify an annotation:

@SuppressWarnings(\"unchecked\")

What does this mean?

Answer 1

It could also mean that the current Java type system version isn't good enough for your case. There were several JSR propositions / hacks to fix this: Type tokens, Super Type Tokens, Class.cast().

If you really need this supression, narrow it down as much as possible (e.g. don't put it onto the class itself or onto a long method). An example:

public List getALegacyListReversed() {
   @SuppressWarnings("unchecked") List list =
       (List)legacyLibrary.getStringList();

   Collections.reverse(list);
   return list;
}